“Assistant” (* out of four) was an exceedingly trashy and unpleasant potboiler about a gullible woman (Kate Palmerston) who goes to work for a woman (Claudine Helen) as her assistant and gradually realizes she is drawn into a serpentine and sleazy web of murder and duplicity. The kind of movie where you want to take a shower almost immediately afterwards; is there anything more dispiriting than trash done with no conviction or flair? Even at only a little more than an hour, this is pretty grueling.